COVID-19: Vaccine side effects and reactions

Find out the side effects, the reported adverse events and allergic reactions to the Pfizer vaccine.

Last updated: 5 May 2021

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How side effects are identified

In the COVID-19 vaccine clinical trials, people were followed very closely for side (adverse) effects for 2 months after the second dose of the vaccine. They compared the results between people who had and hadn’t been vaccinated.

Ongoing monitoring of participants

To understand the vaccine's long-term effectiveness, safety, and side effects, participants in the clinical trials are tracked for another two years. This is from their second dose of the Pfizer vaccine. Participants will:

  • have their health monitored
  • attend regular follow-up visits.

This clinical trial data is closely monitored by Pfizer/BioNTech and an independent group of experts called the Data Monitoring Committee.


Known side effects

Like all medicines, the vaccine may cause side effects in some people. Most side effects are mild and don’t last long. They won’t stop you from having the second dose or going about your daily life.

Some side effects may temporarily affect your ability to drive or use machinery.

Common side effects

In the clinical trials, common side effects were reported in every 1 in 10 to 1 in 100 people. These include:

  • pain or swelling at the injection site
  • feeling tired or fatigued
  • headache
  • muscle aches
  • chills
  • joint pain
  • fever
  • redness at the injection site
  • nausea

Uncommon side effects

In the clinical trials, uncommon side effects were reported in every 1 in 100 to 1 in 1,000 people. These include:

  • enlarged lymph nodes
  • feeling unwell
  • pain in limb
  • insomnia
  • itching at injection site

Rare side effects

In the clinical trials, temporary one-sided facial drooping was reported in every 1 in 1,000 to 1 in 10,000 people.


Allergic reactions

Serious allergic reactions do happen but are extremely rare. They usually show soon after you’ve had your vaccine, which is why you need to wait at least 20 minutes. If you do have a serious allergic reaction, vaccinators are trained to manage these.

If you’ve had an allergic reaction to any vaccine or injection in the past, talk to your vaccinator.


When you’re likely to experience a side effect

Most side effects show within a day or two after being vaccinated.

What you may feel What can help When this could start

Pain at the injection site, a headache and feeling tired and fatigued. These are the most commonly reported side effects.

Place a cold, wet cloth, or ice pack on the injection site for a short time.

Do not rub or massage the injection site.

Within 6 to 24 hours

Muscle aches, feeling generally unwell, chills, fever, joint pain and nausea may also occur.

Rest and drink plenty of fluids

Paracetamol or ibuprofen can be taken, follow the manufacturer’s instructions.

Seek advice from your health professional if your symptoms worsen.

Within 6 to 48 hours

If you’re concerned about how you’re feeling

If you’re unsure about your symptoms or if they get worse, call Healthline:

Phone 0800 358 5453

If you’re concerned about your safety, call 111. Tell them you’ve had a COVID-19 vaccination so they can assess you properly.


Reported side effects in New Zealand

Adverse events following immunisation (AEFI) for the COVID-19 vaccine are reported to the Centre for Adverse Reactions Monitoring (CARM). We commonly know these as side effects.

Any side effects reported are suspected by the reporter to be caused by the vaccine. It doesn’t always mean the vaccine did cause the side effect.

Centre for Adverse Reactions Monitoring (CARM)

Medsafe closely monitors and releases a safety report showing this data each week. This shows the most common side effects that people in New Zealand experience after getting the COVID-19 vaccine.

Latest safety report from Medsafe

Timeframe: 20 February to 3 April 2021
COVID-19 vaccine administered: Pfizer/BioNTech (Comirnaty)
Total doses given: 82,093

Number of reports received on adverse events following immunisation (AEFI)

This shows the number of reports, not the number of people who experienced an adverse event. One person may report on more than one symptom.

  • Total reports received: 663
  • Total reports that were serious: 19
  • Total reports that were not serious: 644
  • Safety signals or potential safety issues identified: 0

The most reported adverse events

Of the 663 total reports, the top 10 reported adverse events were:

  • Headache: 175 reports
  • Dizziness: 169 reports
  • Nausea: 128 reports
  • Pain at the injection site: 91 reports
  • Fever: 52 reports
  • Flu-like illness: 39 reports
  • Muscle pain: 39 reports
  • Fainting: 37 reports
  • Musculoskeletal pain: 34 reports
  • Lethargy: 29 reports

Serious adverse events reported

Of the 19 serious adverse events reported:

  • 15 cases were allergic reactions and were managed appropriately.
  • 2 was a reactogenicity reaction, where the patient experienced flu-like symptoms.
  • 1 was a seizure-type event
  • 1 was chest discomfort and a fast heart rate.

View the full reports

For the full reports, including definitions:

Safety report 5 – 3 April 2021
Safety report 4 – 27 March 2021
Safety report 3 – 20 March 2021
Safety report 2 – 13 March 2021
Safety report 1 – 6 March 2021

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